FB is making sure you can't calculate the ROI of a campaign. Marketers are putting money in FB because they think this is where they can the most accurately target people.
This is demonstrably not true. FB provides better tools than pretty much anyone else to tie sales to advertising (online or off) and to track app instal lifetime advertising revenue generated over time. The human data and walled garden of tracking they have are hugely valuable in proving ROI.
https://adage.com/article/digital/p-g-decided-facebook-ad-ta...
https://www.forbes.com/sites/joannmuller/2012/05/15/gm-says-...